On April 23, 2026, Salesforce filed suit against Microsoft at London's High Court through its workspace messaging platform, Slack. The claim alleges that Microsoft engaged in anticompetitive conduct by tying and bundling Teams with its Microsoft 365 suite, thereby locking out rivals and distorting the market.
A Slack spokesperson described the motivation plainly: "Microsoft's practices harmed competition, using tying and bundling of Teams to limit customer choice."
Microsoft rejected the claim. A company spokesperson said the case "lacks merit," adding: "Slack's lackluster growth, compared to Zoom and Teams, was based on inferior capabilities when COVID-19 hit in 2020, and had nothing to do with Microsoft."
Both positions are well-rehearsed. This is not the first time these arguments have been aired. In 2020, Slack filed a formal complaint with the European Commission, making essentially the same allegation: that Microsoft had used the distribution reach of its dominant Office suite to impose Teams on customers who had never formally chosen it.
That complaint triggered five years of regulatory scrutiny, eventually leading to a September 2025 settlement in which Microsoft agreed to widen the price gap between Teams-included and Teams-excluded licensing tiers. For enterprise plans such as Microsoft 365 E3 and E5, the mandated differential was set at $8.55 (€8.00) per user per month. The EU's own assessment was pointed. Microsoft had been illegally bundling Teams with its Office suite since April 2019.
The settlement was presented as a resolution. What followed complicated that picture. On November 1, 2025, the same month the EU terms came into effect, Microsoft reintroduced Teams-bundled packages globally at their original price points. Teams-excluded pricing was simultaneously reduced, with Office 365 E3 without Teams falling 44 percent to $14.45 per user per month.
This was technically compliant with the EU's requirements. In practice, the global default for most enterprise customers outside the EEA resets to Teams included. Slack's decision to file a UK claim barely two months after that settlement reflects a clear view of how meaningful those concessions were.
The filing also lands alongside two other significant UK legal developments. In the same week, London's Competition Appeal Tribunal certified a separate class action involving close to 60,000 British businesses, which alleges Microsoft overcharged enterprises for Windows Server licenses when running workloads on rival cloud platforms, including AWS, Google Cloud, and Alibaba Cloud, while offering more favorable terms on its own Azure platform. Potential damages are estimated at up to £2.1 billion ($2.8 billion).
